Toll-like receptors (TLRs) recognize and respond to conserved motifs termed “pathogen-associated molecular patterns” (PAMPs). TLRs are characterized by an extracellular leucine-rich repeat motif and an intracellular Toll/IL-1 receptor (TIR) domain. Triggering of TLRs by PAMPs initiates a series of intracellular signaling events resulting in an inflammatory immune response designed to contain and eliminate the pathogen. Viruses encode immunoregulatory proteins, such as A52R (produced by the vaccina virus), that can effectively inhibit intracellular TIR signaling resulting in a diminished inflammatory immune response.
Noise induced hearing loss is the second most common cause of hearing loss. Noise can damage the hair cells in the inner ear and can cause hearing loss, ear ringing and distortion of sounds. Similarly, tissue damage related to aging can cause or exacerbate hearing loss in animals.